Seat assembly having compression limiter with wave portion

ABSTRACT

A seat assembly includes a frame, a seating base layer, a compression limiter layer, a load distribution layer, and an adjustment module. The seating base layer is arranged on the frame. The compression limiter layer is arranged adjacent to the seating base layer and comprises a wave portion forming a knee support. The load distribution layer is connected to the compression limiter layer. The adjustment module is movable between a rear position and a forward position and is configured to move the wave portion between a retracted position and an extended position. The wave portion has one of more first wave elements formed as springs and one or more second wave elements formed as springs. The first wave elements are offset from the second wave elements in a radial direction.

RELATED APPLICATIONS

This application is a continuation of pending U.S. Non-ProvisionalApplication Ser. No. 16/965,145 entitled “Seat Assembly havingCompression Limiter with Wave Portion” filed Jul. 27, 2020, whichrepresents the United States national stage filing of PCT/US2019/019237,filed Feb. 22, 2019, which claims the benefit of U.S. ProvisionalApplication No. 62/633,949, entitled “Seat Assembly having CompressionLimiter with Wave Portion,” with a filing date of Feb. 22, 2018.

BACKGROUND

The following description relates to an adjustable seat assembly for usein automotive applications, office furniture and recreational vehicleseating.

Automotive seating designs have traditionally used common materials andprocesses across manufacturers. Known seating designs typically includesteel frames, steel suspensions and compression limiters, accompanied byfabric or leather trim covers. Compression limiters are most commonlyimplemented in automotive seating as foam layers. Compression limitersare used to distribute reaction forces, diffuse occupant stress spikesand offer controlled deflection under forces resulting in energyabsorption.

In known automotive seating designs, the commonly used foam layers, ascompression limiters, have been found suitable for providing comfort andload distribution, observable in pressure map testing. The comfort offoamed seating (i.e., seating designs including the foam layers) isdetermined, at least in part, by the foam durometer, thickness andporosity to control indentation force deflection (IFD), which is acommonly used measurement to judge and control comfort. The foamedmaterials of the foam layers are typically thermoset materials.

Some automotive seating designs include additional features such as seatheating and/or cooling devices. The heating and cooling devices mayinclude resistive electrical circuitry (for heating) and relatedelectrical component such as wire harnesses and the like, Peltierthermo-electric generators, blowers, fans and the like. In some seatingdesigns, a vacuum generated by a fan blower can provide a coolingsensation to the occupant by pulling air and moisture from the occupantthrough the seat using a manifold system through the foam layers. Insome instances, seating designs include further components configured todampen buzz, squeak and rattle (BSR) of the fan blowers.

Known automotive seating designs may include features to customize seatfit and ergonomic function for individual body shapes and sizes. Forexample, 4-way and 8-way adjustable seats have become common in themarket, and more recently, 33-way adjustable seats have been developed.Adjustable seats of these types articulate using electrical motorizedactuators and air driven bladders. In some designs, pulse actuation isused for providing vibration massage functionality. The foam layerscommonly used in automotive seating designs have been found suitable foraccommodating such adjustability in automotive seating applications,while offering suitable IFD characteristics throughout a range ofpositions during adjustment.

However, the commonly used foam layers tend to be bulky and can occupy asignificant volume in an auto- motive interior. In addition, the foamlayers have inherent insulative characteristics which require additionaldesign considerations in heating and cooling systems to provide adesired level of comfort to a seated occupant. Further, it can bedifficult to integrate additional seating components, including heat andcooling system components, electrical components such as wire-harnesses,seat adjustment modules and other auxiliary components with the foamlayers. Often, these additional components need to be installed under oraround the foam layers, thereby occupying additional volume in theautomotive interior. Further still, common foam materials andchemistries, such as polyurethane foam, may involve the use of regulatedconstituents or other materials which require special handling and/orcare during manufacture. Moreover, in traditional seating designs, thepolyurethane foam is typically supported by steel or other metalsuspension components. However, these materials can be corrosive.

Accordingly, it is desirable to develop an alternative to foamautomotive seating designs to address the drawbacks identified above,while retaining, or improving upon, as many benefits of the foamedseating designs as possible, such as comfort and adjustabilitycharacteristics.

SUMMARY

In one aspect, a seat assembly includes a frame, a seating base layer, acompression limiter layer, a load distribution layer, and an adjustmentmodule. The seating base layer is arranged on the frame. The compressionlimiter layer is arranged adjacent to the seating base layer andcomprises a wave portion forming a knee support. The load distributionlayer is connected to the compression limiter layer. The adjustmentmodule is movable between a rear position and a forward position and isconfigured to move the wave portion between a retracted position and anextended position. The wave portion has one or more first wave elementsformed as springs and one or more second wave elements formed assprings. The first wave elements are offset from the second waveelements in a radial direction.

In another aspect, at least one of the first wave elements form a cupshape in the extended position and form a flat shape in the retractedposition. In another aspect, the compression limiter layer furthercomprises a coil portion that includes a plurality of coil springs. Inanother aspect, the plurality of coil springs extend between the seatingbase layer and load distribution layer. In another aspect, the pluralityof coil springs are attached to the seating base layer or the loaddistribution layer by a plurality of snap-fit connections.

In another aspect, the wave portion has a length measured along a lineor curve, and the length is substantially constant in both the retractedposition and the extended position. In another aspect, the first waveelements are separate, individual springs having a length that extendsalong a width direction and include one or more waves formed along therespective length of the first wave element. In another aspect, thefirst wave elements are formed as substantially linear wave springs. Inanother aspect, the wave portion has a curved profile in the retractedposition and a linear profile in the extended position. In anotheraspect, a first set of trunnions connect the wave portion to the loaddistribution layer. In another aspect, a retainer layer is positionedbetween the wave portion and the adjustment module, and a second set oftrunnions connect the wave portion to the retainer layer.

In another aspect, the first wave elements are closer to the loaddistribution layer than the second wave elements. In another aspect, thefirst wave elements and the second wave elements are configured to moveor slide with respect to the other. In another aspect, a forcedeflection or spring rate of the first wave element may be adjusted byadjusting a wave element width, a wave element shape between a flat orcupped shape, a wave height, a wave pitch, or by a change in a number ofwaves that comprise the first wave element.

In another aspect, a seat assembly has a frame, a seating base layer, acompression limiter layer, a load distribution layer, and an adjustmentmodule. The seating base layer is arranged on the frame. The compressionlimiter layer is arranged adjacent to the seating base layer. Thecompression limiter layer has a coiled portion and a wave portionforming a knee support. The load distribution layer is connected to thecompression limiter layer. The adjustment module is movable between arear position and a forward position and configured to move the waveportion between a retracted position and an extended position. The waveportion includes one or more first wave elements formed as springs andconnected to each other by a first plurality of ribs, one or more secondwave elements connected to each other by a second plurality of ribs, anda first set of trunnions that connect the wave portion to the loaddistribution layer.

In another aspect, the first wave elements are closer to the loaddistribution layer than the second wave elements. In another aspect, thefirst wave elements are separate, individual springs having a lengththat extend along a width direction and include one or more undulationsformed along the respective length of the first wave element.

In another aspect, a seat assembly includes a frame, a seating baselayer, a retainer layer, a compression limiter layer, a loaddistribution layer, and an adjustment module. The seating base layer isarranged on the frame. The compression limiter layer is arrangedadjacent to the seating base layer and has a coiled portion and a waveportion forming a knee support. The load distribution layer is connectedto the compression limiter layer. The adjustment module is movablebetween a rear position and a forward position and is configured to movethe wave portion between a retracted position and an extended position.The wave portion has a first plurality of wave elements connected toeach other by a first plurality of ribs, a second plurality of waveelements formed as springs and connected to each other by a secondplurality of ribs, and a set of trunnions connecting the wave portion tothe retainer layer.

In another aspect, the first wave elements are formed as springs and thesecond wave elements are closer to the retainer layer than the firstwave elements. In another aspect, the first wave elements and the secondwave elements are formed as substantially linear wave springs and aforce deflection or spring rate of one or more of the second waveelements may be adjusted by adjusting a wave element width, a waveelement shape between a flat or cupped shape, a wave height, a wavepitch, or by a change in the number of waves that form the second waveelement.

These and other features and advantages of the present device will beapparent from the following description, taken in conjunction with theaccompanying sheets of drawings, and in conjunction with the appendedclaims.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The benefits and advantages of the present embodiments will become morereadily apparent to those of ordinary skill in the relevant art afterreviewing the following detailed description and accompanying drawings,wherein:

FIG. 1 is bottom perspective view of a seat assembly according to anembodiment described herein;

FIG. 2 is a top perspective view of the seat assembly of FIG. 1;

FIG. 3 is an exploded view of the seat assembly of FIGS. 1 and 2;

FIG. 4 is a schematic illustration of a side of a seat assembly showingthe various layers of the seat;

FIG. 5 is an illustration of an embodiment of a wave portion showingknee support foam replacement in a retracted position around kneeadjustment modules;

FIGS. 6A and 6B illustrate an adjustment module in a rear position (FIG.6A) and in a forward position (FIG. 6B) according to embodiments;

FIGS. 7A and 7B are similar to FIGS. 6A and 6B, showing embodiments ofthe present layered seat configuration;

FIGS. 8A and 8B illustrate one cushion concept in a perspective view,with the load distribution layer removed for ease of illustration, andshowing the compression limiter layer (FIG. 8A); and a perspective viewshowing the load distribution layer (FIG. 8B), according to embodiments;

FIG. 9 is a diagram showing the wave portion as tooled, in asubstantially linear configuration, and as installed in the seatassembly, in a substantially curved configuration, according to anembodiment;

FIG. 10 is a perspective view showing the wave portion installed at aknee-support section of a seat assembly, according to an embodiment;

FIG. 11 is a top view showing left and right wave portions configuredfor independent adjustment on a seat assembly, according to anembodiment;

FIG. 12 is a side view of a compression limiter layer with the waveportion in a retracted position, according to an embodiment;

FIG. 13 is a side view of a compression limiter layer with the waveportion in a fully extended position, according to an embodiment; and

FIG. 14 is a perspective view of a compression limiter layer with thewave portion in a retracted position, according to an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

While the present disclosure is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describedone or more embodiments with the understanding that the presentdisclosure is to be considered illustrative only and is not intended tolimit the disclosure to any specific embodiment described orillustrated.

FIGS. 1 and 2 are bottom and top perspective views, respectively, of aseat assembly 10, according to embodiments described herein. The seatassembly 10 may be constructed as a foamless seat assembly 10. FIG. 3 isan exploded view of the seat assembly 10 of FIGS. 1 and 2. According toan embodiment, the seat assembly 10 may be an automotive seat assemblydesigned for installation and use in automobiles.

With reference to FIGS. 1-3, the seat assembly 10 generally includes aseating base layer 12, a compression limiter layer 14 and a loaddistribution layer 16. In one embodiment, the seating base layer 12 maybe built using an oriented or partially oriented block copolymer, suchas a thermoplastic elastomer (TPE). The compression limiter layer 14, aswill be described further below, generally includes a coil portion 18and a wave portion 20. The load distribution layer 16 may be arrangedover the compression limiter layer 14 and is configured to distribute aload, for example, from an occupant seated on the seat assembly 10,across the compression limiter layer 14. A retainer layer 22 may underlyat least a portion of compression limiter layer 14, for example, at thewave portion 20.

The seat assembly 10 may further include a frame 24, an adjustmentmodule 26 and a bolster 28. The frame 24 may be configured forconnection to an automotive vehicle body or frame. The adjustment module26 is configured to adjust a position of a seating component, asdescribed below. The bolster 28 may be included in the seat assembly 10to provide a variable reaction spring force that substantially mimicscomfort characteristics (e.g., IFD) of traditional foam seatingcomponents, but can be formed by injection molded thermoplastics inknown injection molding processes. In some embodiments, the bolster 28may extend over rigid or angled seating components to limit occupantexposure to such components and improve comfort. In one embodiment, theseat assembly 10 may also include a manifold membrane 30. The manifoldmembrane 30 may be used with, for example, heating and/or coolingsystems (not shown) of the seat assembly 10.

FIG. 4 is a diagram showing an exploded side view of the seat assembly10, with some components shown schematically, according to anembodiment. In one embodiment, the seat assembly 10 may include a trimcover 32, such as leather or fabric, disposed over the load distributionlayer 16. In one embodiment, the seat assembly 10 may include heatingand/or cooling systems, which may include, for example, a heater mat 34disposed under the load distribution layer 16, a vent blower 36 and awire harness 38 which may be disposed, for instance, under the seatingbase layer 12 and adjacent to or within the frame 24. However, thesecomponents are not limited to such positions.

According to an embodiment, the coil portion 18 of the compressionlimiter layer 14 generally extends along a section of the seat assembly10 where an occupant is seated, i.e., where a substantially verticalcomponent of an occupant's weight will be applied to the seat assembly10. The coil portion 18 may be formed by a plurality of coil springsextending between the seating base layer 12 and the load distributionlayer 16. The coil springs may be attached to the seating base layer 12and/or the load distribution layer 16, for example, by a plurality ofsnap-fit connections or other suitable attachment mechanisms.

The wave portion 20 of the compression limiter layer 14 may generallyextend over a knee-support section of the seat assembly 10, designed tosupport an underside or back of an occupant's knee when the occupant isin a seated position. Thus, in at least one configuration, the waveportion 20 may be extend generally in linear helical shape, around acenter of curvature. For example, as shown in FIG. 4, in the side view,the wave portion 20 may extend as a curved segment generally in aC-shape.

In one embodiment, the adjustment module 26 may be a knee support moduleconfigured to adjust a position of the knee-support section of the seatassembly 10. For example, as described further below, the adjustmentmodule 26 may be actuated to move the wave portion 20. In oneembodiment, the adjustment module 26 includes an actuator 40 operablyconnected to a body 42. The actuator 40 can be operated to drive thebody 42 to adjust the position of the knee-support section.

FIG. 5 is an enlarged perspective view of the seat assembly 10 showingthe compression limiter layer 14, including the wave portion 20 at theknee-support section, according to an embodiment. The wave portion 20may be substantially linear in overall shape, for example, extending awidth direction ‘W’ of the seat assembly 10. The wave portion 20includes a plurality of wave elements 44, 46. In one embodiment, theplurality of wave elements includes one or more first wave elements 44and one or more second wave elements 46. In one embodiment, a pluralityof first and second wave elements 44, 46 are provided, and individualfirst and second wave elements 44, 46 are alternately positioned withrespect to one another along a length direction or direction ofcurvature. In one embodiment, the first and second wave elements 44, 46may be offset, or staggered, from one another in radial direction orthickness direction. For example, the first wave elements 44 may berelatively outwardly positioned (i.e., closer to an exterior of the seatassembly 10 or the load support layer 16) and the second wave elements46 may be relative inwardly positioned (i.e., closer to the retainerlayer 22 or the adjustment module 26). In one embodiment, the waveelements 44, 46 may be made from a thermoplastic material.

In one embodiment, the wave elements 44, 46 of the first and second waveelements may be formed as separate, individual springs and may include,for example, one or waves or undulations formed along their respectivelengths (the lengths of the wave elements 44, 46 extend in the widthdirection W of the seat assembly 10 in FIG. 5). That is, the waveelements 44, 46 may be formed as substantially linear wave springs. Inanother embodiment, the individual wave elements 44, 46 may includecup-shaped portions or may be substantially flat. The wave elements 44,46 may be connected to one another by one or more ribs 48. The ribs 48are configured to flex when needed, for example, during adjustment ofthe knee-support section as described further below, thereby allowingmovement of the first and second wave elements 44, 46.

In one embodiment, the first wave elements 44 may be connected to theload distribution layer 16 by one or more snap-fit connections or othersuitable connections. For example, the first wave elements 44 mayinclude one or more trunnions 50 or other suitable projectionsconfigured for snap-fit engagement with an underside of the loaddistribution layer 16. Similarly, the second wave elements 46 may beconnected to the retainer layer 22 by one or more trunnions (not shown)or similar suitable projections configured for snap-fit engagement withthe retainer layer 22. However, the present disclosure is not limited tosuch snap-fit engagements, and other suitable connections areenvisioned.

FIGS. 6A and 6B are side views of the seat assembly 10 with theadjustment module 26 in a rear (or retracted) position (FIG. 6A) and aforward (or extended) position (FIG. 6B), according to embodiments ofthe present disclosure. As shown in FIGS. 6A and 6B, to adjust aposition of the knee-support section of the seat assembly 10, theactuator 40 is operated to move the body 42 outward from the position inFIG. 6A to the position in FIG. 6B to extend a length of theknee-support section. Conversely, the actuator 40 may be operated tomove the body 42 inward from the position in FIG. 6B to the position inFIG. 6A to reduce a length of the knee-support section.

FIGS. 7A and 7B are side views of the seat assembly 10 having theretainer 22 and compression limiter layer 14, including the wave portion20, positioned over the adjustment module 26 (see FIGS. 6A, 6B), withthe adjustment module 26 in the rear (retracted) position (FIG. 7A) andthe forward (extended) position (FIG. 7B), according to embodiments ofthe present disclosure. The wave portion 20, including the first andsecond wave elements 44, 46 (see FIG. 5), is configured such thatmovement of the adjustment module 26 from the rear position to forwardposition, and vice versa, causes the wave portion 20 to slide along asurface of the body 42 without binding, wrinkling or loosing desired orcustomer-specified IFD requirements. Therefore, the compression limiterlayer 14, by way of the wave portion 20 of the embodiments describedherein, can provide consistent comfort in all positions of adjustmentmodule 26. The retainer layer 22 is configured for sliding movementrelative to a surface of the body 42 with the wave portion 20.

The sliding movement of the wave portion 20 is provided by thearrangement of the first and second wave elements 44, 46, which areprovided separately from one another, and are configured to moveindependently of one another. Thus, during sliding movement of the waveportion 20, individual first and second elements 44, 46 may be moverelative to one another.

Referring still to FIGS. 7A and 7B, the wave portion 20 is in aretracted position when the adjustment module 26 is in the rear position(FIG. 7A). In the retracted position, the wave portion 20 has asubstantially curved profile in the side view. Movement of theadjustment module 26 to the forward position moves the wave portion 20to an extended position (FIG. 7B). In the extended position, accordingto one embodiment, the wave portion 20 is at least partiallystraightened, i.e., moved toward a linear profile from the curvedprofile, in the side view. As a result of the sliding movement of thewave portion 20 relative to the body 42, a free end 52 of the waveportion 20 changes position relative to a surface of the body 42.Conversely, movement of the adjustment module 26 from the forwardposition to the rear position causes movement of the wave portion 20from the extended position to the retracted position. In addition, waveshape and load displacement can be maintained throughout adjustment.

FIGS. SA and 8B are perspective views showing the seat assembly 10 withthe load distribution layer 16 removed, to more clearly illustrate thecompression limiter layer 14 (FIG. SA) and with the load distributionlayer 16 installed (FIG. 8B), according to embodiments described herein.In one embodiment, the load distribution layer 16 includes a pluralityof shaped segments 54 connected to another. In one embodiment, eachsegment 54 may be connected to the compression limiter layer 14, forexample, by a snap-fit connection. In this manner, pressure applied tothe load distribution layer 16 may be distributed across the segments 54and the compression limiter layer 14 to obtain desirable IFDcharacteristics and pressure maps.

FIG. 9 is a diagram showing the wave portion 20 as tooled, in asubstantially linear configuration, and as installed on the seatassembly 10, in a substantially curved configuration, similar to theretracted position described in the embodiments above. As shown in FIG.9, in one embodiment, a thickness of the second wave elements 46 maygradually decrease moving toward the free end 52 of the wave portion 20.

FIG. 10 is a perspective view showing the wave portion 20 installed at aknee-support section of a seat assembly 10, according to an embodiment.

FIG. 11 is a top view showing left and right wave portions 20L, 20Rconfigured for independent adjustment on a seat assembly 10, accordingto an embodiment. In one embodiment, the seat assembly 10 may includeindependently adjustable left and right knee-support sections. To thisend, separate left and right wave portions 20L, 20R may be provided.Although not shown in FIG. 11, it is understood that separate left andright adjustment modules 26 can be provided as well and can be operatedindependently of each other.

FIG. 12 is a side view of the compression limiter layer 14 with the waveportion 20 in the retracted position and FIG. 13 is a side view of thecompression limiter layer 14 with the wave portion 20 in a fullyextended position, according to embodiments described herein. Asdescribed above, and shown in FIG. 12, in the retracted position, thewave portion 20 may have a substantially curved profile in the side viewand may be shaped as a linear helix. In a fully extended position, asshown in FIG. 13, the wave portion 20 may be arranged in a substantiallylinear or planar configuration. The wave elements 44, 46 are configuredfor movement during adjustment such that stretching or pinching of atrim cover 32 is substantially limited or prevented while the waveelements 44, 46 provide a cushioning effect and desirable IFD compliancethroughout the adjustment. In one embodiment, a length 1′ of the waveportion 20, measured along a line or a curve, may be substantiallyconstant during movement of the wave portion 20 between the retractedand extended positions because of the sliding motion of the waveelements 44, 46. In one embodiment, this feature may be accommodated, atleast in part, by independent relative movement of the individual waveelements 44, 46 during adjustment.

FIG. 14 is a perspective view of the compression limiter layer 14 withthe wave portion 20 in the retracted position, according to anembodiment. As described in the embodiments above, the first and secondwave elements 44, 46 may be alternately positioned relative to oneanother and offset or staggered.

In the embodiments above, the design of the wave portion 20 maintains acommon length of line at a class A interface where the trim cover 32contacts the load distribution layer 16. The length of line design ruleenables the wave portion to fold and expand (i.e., retract and extend)during adjustment without wrinkling or overstretching the trim cover 32.The length of line positioning also enables manufacturers to remove andreplace trim covers 32, and/or use the load distribution layer 16 is anoccupant interface.

The seat assembly 10 of the embodiments described herein, in whichconventional foam layers are replaced with the compression limiter layer14 including the wave portion 20, may allow for seats to be produced atreduced costs, occupy a smaller volume, provide more breathable occupantseating interfaces, avoid absorption of fluids, be easily cleaned andcan reduce emissions by using inert thermoplastic materials.

The embodiments described herein, including the compression limiterlayer 14 having the wave portion 20, may also permit varying thethickness and profile shape of the seat throughout seating adjustment.Seating shapes utilizing suspension tension members have traditionallybeen limited to one-dimensional (ID) variable profiles by altering thetension frame shape. However, two-dimensional (2D) seat surface profileshave been limited when using suspension only. Materials that offercompression limiter function and physical thickness like foams or coilssprings can offer 2D profiles to seat stylists, but are limited whenwrapping around actuated radiuses, such as at knee-support sections. Asillustrated in FIGS. 5, 6A, 6B, 7A and 7B, wave portion 20 describedherein allows several millimeters of actuator travel while maintainingseat shape, and IFD compliance for comfort.

The wave portion 20 is also adaptable to different customer requirementsthrough a wide range of tuning mechanisms. For example, force deflectionor spring rate may be tuned by adjusting wave element width, waveelement shape (flat vs. cupped), wave element material, modulusperformance, top (outer) wave vs. bottom (inner) wave height and wavepitch and sign wave frequency (number of waves), and other inputs.

It has been found that the embodiments of the seat assembly 10 describedherein are capable of providing an IFD compliant design that mimics oroutperforms foam materials used in conventional automotive seatingapplications during most or all adjustment positions. The adjustmentshighlighted in FIGS. 6A-6B and 7A-7B show an example of a range ofactuated adjustment (for example, a 50 mm-100 mm range) for occupantpositioning within a 33-way adjustable seat.

It should also be understood that various changes and modifications tothe presently disclosed embodiments will be apparent to those skilled inthe art. Such changes and modifications can be made without departingfrom the spirit and scope of the present disclosure and withoutdiminishing its intended advantages. It is therefore intended that suchchanges and modifications be covered by the appended claims. It isfurther understood that various features from the embodiments describedabove and shown in the drawings may be combined with other embodimentsdescribed herein and shown in the drawings.

1. A seat assembly, comprising: a frame; a seating base layer arrangedon the frame; a compression limiter layer arranged adjacent to theseating base layer, the compression limiter layer comprising a waveportion forming a knee support; a load distribution layer connected tothe compression limiter layer; and an adjustment module movable betweena rear position and a forward position and configured to move the waveportion between a retracted position and an extended position, whereinthe wave portion comprises one of more first wave elements formed assprings and one or more second wave elements formed as springs, whereinthe first wave elements are offset from the second wave elements in aradial direction.
 2. The seat assembly of claim 1, wherein at least oneof the first wave elements form a cup shape in the extended position andform a flat shape in the retracted position.
 3. The seat assembly ofclaim 1, wherein the compression limiter layer further comprises a coilportion that includes a plurality of coil springs.
 4. The seat assemblyof claim 3, wherein the plurality of coil springs extend between theseating base layer and load distribution layer.
 5. The seat assembly ofclaim 4, wherein the plurality of coil springs are attached to theseating base layer or the load distribution layer by a plurality ofsnap-fit connections.
 6. The seat assembly of claim 1, wherein the waveportion has a length measured along a line or curve, and the length issubstantially constant in both the retracted position and the extendedposition.
 7. The seat assembly of claim 1, wherein the first waveelements are separate, individual springs having a length that extendsalong a width direction and include one or more waves formed along therespective length of the first wave element.
 8. The seat assembly ofclaim 7, wherein the first wave elements are formed as substantiallylinear wave springs.
 9. The seat assembly of claim 1, wherein the waveportion has a curved profile in the retracted position and a linearprofile in the extended position.
 10. The seat assembly of claim 1,wherein a first set of trunnions connect the wave portion to the loaddistribution layer.
 11. The seat assembly of claim 10, wherein aretainer layer is positioned between the wave portion and the adjustmentmodule, and a second set of trunnions connect the wave portion to theretainer layer.
 12. The seat assembly of claim 1, wherein the first waveelements are closer to the load distribution layer than the second waveelements.
 13. The seat assembly of claim 1, wherein the first waveelements and the second wave elements are configured to move or slidewith respect to the other.
 14. The seat assembly of claim 1, wherein aforce deflection or spring rate of the first wave element may beadjusted by adjusting a wave element width, a wave element shape betweena flat or cupped shape, a wave height, a wave pitch, or by a change in anumber of waves that comprise the first wave element.
 15. A seatassembly comprising: a frame; a seating base layer arranged on theframe; a compression limiter layer arranged adjacent to the seating baselayer, the compression limiter layer comprising a coiled portion and awave portion forming a knee support; a load distribution layer connectedto the compression limiter layer; and an adjustment module movablebetween a rear position and a forward position and configured to movethe wave portion between a retracted position and an extended position,wherein the wave portion comprises one or more first wave elementsformed as springs and connected to each other by a first plurality ofribs, one or more second wave elements connected to each other by asecond plurality of ribs, and a first set of trunnions connecting thewave portion to the load distribution layer.
 16. The seat assembly ofclaim 15, wherein the first wave elements are closer to the loaddistribution layer than the second wave elements.
 17. The seat assemblyof claim 16, wherein the first wave elements are separate, individualsprings having a length that extend along a width direction and includeone or more undulations formed along the respective length of the firstwave element.
 18. A seat assembly comprising: a frame; a seating baselayer arranged on the frame; a retainer layer; a compression limiterlayer arranged adjacent to the seating base layer, the compressionlimiter layer comprising a coiled portion and a wave portion forming aknee support; a load distribution layer connected to the compressionlimiter layer; and an adjustment module movable between a rear positionand a forward position and configured to move the wave portion between aretracted position and an extended position, wherein the wave portioncomprises a first plurality of wave elements connected to each other bya first plurality of ribs, a second plurality of wave elements formed assprings and connected to each other by a second plurality of ribs, and aset of trunnions connecting the wave portion to the retainer layer. 19.The seat assembly of claim 18, wherein the first wave elements areformed as springs and the second wave elements are closer to theretainer layer than the first wave elements.
 20. The seat assembly ofclaim 19, wherein the first wave elements and the second wave elementsare formed as substantially linear wave springs and a force deflectionor spring rate of one or more of the second wave elements may beadjusted by adjusting a wave element width, a wave element shape betweena flat or cupped shape, a wave height, a wave pitch, or by a change inthe number of waves that form the second wave element.